Canadian researchers suggest that retinal function could prove to be a useful biomarker for detecting the risk of schizophrenia and bipolar disorder.
Lead researchers Marc Hebert, Michel Maziade claim that retinal deficits may contribute to the perceptual problems associated with the disorders.
Over the past several years, research has suggested that cognitive impairments in schizophrenia might be linked to early stages of visual perception.
This work is now drawing attention to the function of the retina, the component of the eye that detects light.
Within the retina, rods are light sensors that respond to black and white, but not to colour. Rods are particularly important for maintaining vision under conditions of low light and for detecting stimuli at the periphery of vision. Cones are light sensors that detect colour and perceive stimuli at the centre of vision.
With help of electroretinography (ERG), a specialized measure of retinal function, the researchers observed that the ability of light to activate rods was significantly reduced in currently healthy individuals who descended from multigenerational families that had members diagnosed with either schizophrenia or bipolar disorder.
In contrast, the response of their cones to light was normal.
"We take for granted that other people experience the world in the same way that we do," said Dr. John Krystal, Editor of Biological Psychiatry.
"It is important to appreciate that for schizophrenia and bipolar disorder, as for colour-blindness or selective hearing loss, people who appear to perceive the world normally may actually have subtle but important problems with perception, which may contribute to other adaptive impairments," he added.
The study appears in journal Biological Psychiatry.